Most people are familiar with Dr. Martin Luther King’s “I’ve Been to the Mountaintop” speech, but many don’t know the speech he delivered the night before his assassination was delivered to striking sanitation workers.

Some civil rights movement history was going up for auction Thursday in New York City. Papers from the Rev. Martin Luther King Jr. were being sold by Maude Ballou, 88, who worked as King’s secretary from 1955 to 1960.